The application of steering and braking systems is widely applied to utility vehicles, particularly agricultural vehicles, such as, for example, tractors or the like. The steering and braking system permits the control of the direction of operation of the motor vehicle beyond the effect of a conventional stub axle steering control.
The principle of the steering and braking system relies upon a change or a repositioning of the distribution of the braking or driving forces between the two sides of the motor vehicle. The distribution of the braking or driving forces is performed in such a way that a yaw moment supporting the immediate direction of operation is built up in the direction of the vertical axis of the motor vehicle. In the simplest case at least one of the vehicle wheels is braked on one side of the motor vehicle, while the remaining vehicle wheels remain not braked. In this way a reduction of the turning circle diameter, in particular, can be attained during the performance of a turning maneuver.
Such a steering and braking system for a motor vehicle is known from DE 27 50 851 A1. The steering and braking system is a component of a hydraulic operating brake system of a motor vehicle. The hydraulic operating brake system includes several hydraulic wheel brake cylinders for braking associated vehicle wheels, where the wheel brake cylinders can be controlled by the operator by means of brake pedal. To perform a steering and braking process the wheel brake cylinders of at least each of the rear wheels of the motor vehicle can be controlled separately by actuation of the associated hand brake levers. Since the operator must manually actuate both hand brake levers of the steering and braking system, the performance of the steering and braking process is comparably uncomfortable.
A comparable steering and braking system is disclosed by DE 101 45 789 A1. In place of manual brake levers, separate brake pedals are provided for the performance of the steering and braking process, where for operation on public roads, the brake pedals can be connected mechanically with each other.
Furthermore, EP 275 985 A2 discloses a steering and braking system for a tractor. The supply of the brakes with hydraulic fluid is performed by a pedal-operated master-cylinder that can be connected selectively over intervening electrical positioning systems with a brake cylinder of a right and/or a left driven vehicle wheel. An electrical switch contact system is used to recognize a steering angle existing at the steerable vehicle wheels. The electrical switch contact system interacts with the electrical positioning system in such a way that the connection between either the right or the left connection between the master cylinder and the brake cylinder is blocked. The performance of the steering and braking process is therefore exclusively possible in such operating conditions, in which a braking of the tractor is performed simultaneously by actuation of the brake cylinder by the operator. Therefore. the flexibility of the steering and braking systems is comparatively limited.